Figure 1 Effects of buprenorphine, heroin and naloxone on the mu opioid receptor

Figure 1

NB: The mu receptor is one of the primary sites for the reward effects of opiate drugs in the brain. The opiate binds to the affinity zone of the receptor and stimulates the activity zone, thereby producing an effect. In the diagram, heroin, buprenorphine and naloxone are represented by blue polygons, and the receptors by yellow polygons. The stimulatory effect of each chemical is related to how it interacts with the affinity zone (represented here as filling a proportion of the affinity zone). Heroin, classified as a full receptor agonist (stimulator), almost fills the activity zone while buprenorphine, a partial receptor agonist, fills a smaller proportion of it and naloxone does not stimulate the receptor at all. The substances also differ in how strongly they bind to the receptors. A substance that binds more strongly to the receptor can displace a substance that binds less strongly. Thus, buprenorphine can displace both naloxone and heroin, and naloxone can displace heroin.

Source: Adapted from Jones, H. E. (2004), 'Practical considerations for the clinical use of buprenorphine', Science & Practice Perspectives 2, no. 2, pp. 4-20.